CRISPR is a revolutionary genetic editing technique that has been rocking the world of biology ever since researchers first realized they could use it to edit the genome of any species with ease and precision never possible before.

At U of T, Moffat is using CRISPR to identify the set of genes that are essential for cell survival.

"It gives you the tools to ask questions about what things are doing that we could never do before," he said. "It's really exciting."

Scientists are now using CRISPR in a range of wild experiments. They've already designed a mechanism that could wipe out mosquitoes. And they're also toying with using it to bring the woolly mammoth back to life.

It's a tool so powerful, it could be used to permanently alter the human genome in a way that could be passed on to future generations.

Earlier this year, scientists from around the world gathered for an unprecedented summit in Washington, D.C., and agreed to avoid using CRISPR for human genetic engineering

CRISPR against cancer

But what can CRISPR do in research on cancer? That's the question that will be asked in these human trials.

CRISPR is not a therapy on its own. It's a tool. But because of its precision, researchers are hoping it will be able to make genetic edits that are more effective than the traditional gene-editing techniques, to trigger a patient's immune system to kill cancer cells.

'These first tests, if done properly, are going to pave the way for how to use CRISPR to treat disease,' says University of Toronto cancer researcher Jason Moffat. (CBC)Both the U.S. and the Chinese teams intend to use CRISPR in similar ways, but on different cancers. The Chinese will target non-small-cell lung cancer; the U.S. team will work on melanoma, sarcoma and myeloid cancers.

They will harvest a type of immune cell, known as T cells, from a patient's blood and then use CRISPR to tinker with a particular gene in a way that will activate the T cells to attack cancer cells. And then they will put the CRISPR-ed cells back into the patient's body to destroy tumours.

"These first tests, if done properly, are going to pave the way for how to use CRISPR to treat disease," said Moffat.

What risks getting lost in the excitement over these first CRISPR trials is the sobering fact that it might not work. There is the ever-present risk of unintended consequences, including CRISPR's tendency to make unpredictable genetic edits in unwanted places.

And experiments to genetically alter cells and reprogram the immune system are inherently risky. There's a danger of triggering a catastrophic immune response known as a cytokine storm that can fatally overwhelm the body. And by unleashing T cells against cancer, it's also possible they'll start attacking normal tissue, too.

Gene therapy tragedy

In this illustration of CRISPR-CAS9, the Cas9 nuclease protein (white) uses a guide RNA (pink) sequence to cut DNA (green). (Science Photo Library/Getty) For years, the entire field of gene therapy was haunted by an experiment that went tragically wrong in 1999. That's when an Arizona teenager died suddenly, after volunteering to be part of a gene therapy trial to correct a genetic defect that, in his case, was not life-threatening. Many believe the death set back gene therapy research for years.

And last month, a clinical trial testing the same T cell approach, but without using CRISPR, was shut down by the FDA after several patients died. The trial has since been allowed to resume.

The Chinese scientists have secured all the necessary approvals and are scheduled to begin their trial using CRISPR-edited cells in 10 lung cancer patients next month. The U.S. team still needs FDA approval, and they expect to start their trial on 18 patients later this year.

Another caveat: These are Phase 1 trials only. That means the scientists are studying toxicity and side-effects and basic biological responses. Even if all goes well, the trials to see if the approach actually works against cancer are still many years away.

About the Author

Kelly Crowe

Medical science

Kelly Crowe is a medical sciences correspondent for CBC News, specializing in health and biomedical research. She joined CBC in 1991, and has spent 25 years reporting on a wide range of national news and current affairs, with a particular interest in science and medicine.